Deschutes River diversion starts at Colorado Ave. dam

Jan 15, 2015

Bend Bulletin

Bend park district project moving to next phase

By Scott Hammers

The safe passage project at the Colorado Avenue dam on the Deschutes River entered a new phase this week, with contractors preparing to divert the full river into a narrow channel alongside Miller’s Landing Park.

The $9.7 million Bend Park & Recreation District project began in late October. Funded as part of a $29 million bond package approved by voters in 2012, the project is intended to create a safe way for floaters to pass over the dam and a whitewater play area for more experienced paddlers.

Over the last two months, crews have divided the river into two channels separated by a line of sheet piling, long strips of steel pounded into the river bottom.

Tuesday night, sandbags that had been upstream of the Colorado Avenue bridge were removed, allowing water to begin returning to the Miller’s Landing Park channel, which has been relatively dry in recent weeks.

Over the next two weeks, a second wall of sheet piling will be constructed upstream of Colorado Avenue. Starting from near the point where floaters have historically exited the river to avoid the dam, the wall will force the river north into the narrower channel once it’s completed.

Project manager Chelsea Schneider with the park district said most of the work over the next two weeks will be done at night, with regular closures and detours for drivers traveling Colorado Avenue. Downstream, day by day, the wider channel near McKay Park will begin drying out, she said, while the narrow channel by Miller’s Landing Park will run faster and deeper.

“It’s going to change every day over the next couple of weeks,” she said.

Once the wider channel is largely water-free, crews will divide it in half again, creating the gentle safe passage channel close to the river’s edge, and a whitewater play channel in the center. The whitewater area will include steep drops, and a series of pneumatically controlled bladders that can create standing waves and other features.

To prepare for diverting the full flow of the river into a channel roughly one-third as wide as normal, the shoreline between Miller’s Landing Park and the dam has been reinforced.

Schneider said much of the riverbank and river bottom in the area has been covered with a thick rubber mat. Upstream, the mat has been covered with a mound of large rocks, while downstream, the mat is weighed down with large sandbags.

The mat, rocks — riprap in engineering terminology —and sandbags should protect delicate riparian areas from washing away once the river is diverted. She said the reinforcement is more robust than it probably needs to be, and the river is not expected to rise dramatically — but, in the event of rising waters, the bulked-up banks should keep the river in the channel.

“You won’t see the water come all the way to the top of that riprap, but at the bottom of that riprap, that’s where it should be,” she said.

Once the safe passage and whitewater areas are completed, the river will be diverted to pass through those channels, drying out the channel on the Miller’s Landing side to allow for construction of a slow-moving habitat area that will provide sanctuary for small fish and amphibians.